The present invention relates to devices for indicating when the sharpened end of a needle has penetrated through bodily tissue into a lumen or other bodily cavity.
Certain medical procedures require the penetration of veins, arteries, or other bodily lumens by needled catheters. For example, drawing blood requires that a needle be stabbed into an artery or vein to provide a guide for insertion of a catheter which functions as a channel for the evacuation of blood. During a tracheotomy, a hollow needle is stabbed into the trachea to afford a channel and entry for a catheter, which opens a free passage for breathing.
It can be difficult to correctly determine the location of the end of the needle that is being inserted through bodily tissue into a cavity. When a blood vessel is being punctured, it is sometimes possible to detect proper penetration of the vessel by the presence of blood, if the hydraulic pressure in the vessel is sufficient to move blood through the needle. However, this may not work in the case of a vein where the fluid pressure is lower than in an artery. Of course there is no movement of fluid to signal the successful insertion of a needle into a trachea.
As is known, if there is no reliable indication of penetration, it is possible for a vessel or a lumen to be completely transfixed, with a needle passing completely through both walls of a vessel without giving any indication of having travelled through it. Complete transfixation most often happens in small vessels or in vessels whose walls flatten under pressure from a needle. In such cases, before it penetrates the near vessel wall, a needle will force the near wall against the far wall; if penetration occurs suddenly, the momentum of the needle can carry it through both the near and the (now near) far wall.
It would therefore be desirable to provide an instrument and a technique for indicating to a nurse, medical technician, or physician when the sharpened end of a needle has penetrated one wall and entered the interior of a lumen, with the indication being given quickly enough to prevent the end being pushed completely through the lumen. It would also be desirable for such an instrument to reduce the likelihood of completely transfixing a vessel by blocking the sharpened end from the back wall of the vessel once the vessel's front wall is penetrated.